Ground burrowing device



K. J. ZYGMUNT GROUND BURROWING DEVICE 2 Sheets-Sheet 1 Filed Oct. 18. 1986 INVENTOR KA Z/M/ERZ JUL wvZmMu/v T BY gmjc ATTORNEYS Oct. 28, 1969 I ZYGMUNT 3,474,873

GROUND BURROWING DEVICE I Filed Oct. 18, 1966 2 Sheets-Sheet 2 FIG. 4 FIG. 5.

FIG. 9

\ U IIII--III INVENTOR KA Z/M/ERZ JUL IAN Z YGMU/V T RNEYS United States Patent 3,474,873 GROUND BURROWING DEVICE Kazimierz Julian Zygmunt, 78 Chrzanowskiego St., Gdansk-Wrzeszcz, Poland Filed Oct. 18, 1966, Ser. No. 587,524

Int. Cl. E21b 11/02 US. Cl. 175--19 6 Claims ABSTRACT OF THE DISCLOSURE A ground burrowing device having all movable driving elements enclosed within an elongated outer casing with a removable expander member releasably positioned on the outer casing in encircling relationship therewith for movement off the forward end of the casing, the expander member having an inner dimension at least equal to the outer dimension of the casing and an outer dimension greater than the maximum outer dimension of the casing.

The present invention relates to a power driven, projectile shaped ground burrowing device for burrowing a hole through the ground in which the driving mechanism is contained, wholly within the device and actuated by compressed air fed from a source outside the burrowed hole. More particularly, the present invention relates to a burrowing device constructed to produce a hole of a cross-sectional dimension greater than that of the projectile portion of the device so as to facilitate retraction of the device rearwardly through the burrowed hole after the burrowing operation has been completed.

The ground burrowing devices to which the present invention is directed are disclosed in US. Patent No. 3,137,483 granted June 16, 1964. Generally, these devices include an outer casing in which all the movable driving elements are enclosed. The casing itself is shaped somewhat like a projectile and is provided in the interior thereof with an air chamber. A drive piston is slidably mounted within this chamber and is adapted to be driven from one end of the chamber to the other by means of compressed air fed to the device through its rear end. An anvil wall is provided internally of the casing against which the piston is adapted to strike. The force of the piston striking this wall forces the burrowing device as a unit in the same direction as the movement of the piston as the latter makes contact with the wall.

These burrowing devices may be of two types. One type is provided with only one anvil wall in the chamber. This wall faces rearwardly of the device and when the device is operated, the piston, by striking the anvil wall, forces the burrowing device forwardly through the ground to burrow a hole. In some situations, as for example where it is desired to burrow a hole under a roadway, a vertical hole may be dug into the ground on either side of the road. Where this is done, the ground burrowing device may be lowered into the vertical hole on one side of the roadway and aimed toward the vertical hole on the other side. Assuming that the burrowing device has been properly aimed, it may be removed from the second vertical hole after transversing under the roadway.

In some situations, however, it is more advantageous to remove the ground burrowing device from the burrowed hole by retracting it through the hole. With the type of device that is power actuated in only the forward direction, this may be effected by attaching a cable to the rear end of the device. This cable will be played out as the device burrows its hole and when the burrowing operation has been completed, the device may be retracted through the formed hole by pulling on the cable.

3,474,873 Patented Oct. 28, 1969 "ice In the second type of burrowing device mentioned above, an anvil wall is provided at either end of the internal chamber and a suitable control is included for repeatedly driving the piston against either one or the other of these walls. With this construction, the device may be retracted through the burrowed hole under its own power.

With each of these two constructions, the burrowed hole that is formed by the device, is, of course, of the same cross-sectional size as that of the device itself. Accordingly, when it is desired to retract the device through the burrowed hole after the burrowing operation has been completed, the wall surface of the burrowed hole tends to restrict the movement of the device, and if the edge of a rock, disposed along the wall of the burrowed hole is engaged by the burrowing device as it is being retracted, it will tend to interfere with further rearward movement of the device along the path defined by the hole and perhaps even tend to turn the device within the burrowed hole into a skewed position. It is apparent that such .a result might jam the burrowing device within the burrowed hole whereby further pulling on the cable if the device is one which is power actuated in only the forward direction could cause the cable to break away from the device with the result of losing the burrowing device. Also, if the device is one that is power actuated in both directions, driving it rearwardly from its skewed position might cause it to start off on a new path.

According to the teachings of the present invention, the possibility of these undesirable results occurring is effectively eliminated. Specifically, the improved ground burrowing device of the present invention includes a projectile shaped burrowing device with an expander sleeve member releasably positioned over the outer casing of the device. The outer dimension of the expander member is made greater than that of the device itself so that the size of this expander member will control the size of the hole burrowed and thereby produce a hole that is of a size larger than that of the burrowing device. In order to take advantage of this increased size, the expander member is releasably positioned on the outer casing of the burrowing device in such a way whereby it will be locked thereon as the device is driven forwardly but will be automatically removed from the device as it is being retracted through the burrowed hole if any great resistance to such retraction is encountered. Of course, if little or no resistance is encountered during this retracting movement of the burrowing device, the expander member may remain in position on the outer casing without hindering such retraction; and in such a case, the expander member may be reused. In the situation where resistance is encountered, however, removal of the expander member will decrease the outer dimension of the burrowing device and thus facilitate its rearward movement since it is now of a dimension less than that of the burrowed hole.

A more complete understanding of the present invention will be obtained from the reading of the following detailed description with reference being made to the accompanying drawings of which:

FIG. 1 is a partial sectional view of the rear portion of the device of the present invention showing the expander member in operating position;

FIG. 2 is a partial sectional view of the front portion of the device shown in FIG. 1; and

FIG. 3 is a cross-sectional view of the expander member;

FIG. 4 is a partial cross-sectional view of a modified embodiment of the expander member positioned on the burrowing device;

FIG. 5 is a partial cross-sectional view of still another modified embodiment of the expander member positioned on the burrowing device;

FIG. 6 is a front end view of a modified embodiment of the piston element of the burrowing device;

FIG. 7 is a front end view of another modified embodiment of the piston;

FIG. 8 is an enlarged partial cross-sectional view of the forward end of the sleeve member of the burrowing device; and

FIG. 9 is an enlarged partial cross-sectional view of the rear end of the piston element of the burrowing device.

As shown in FIGS. 1 and 2, the ground burrowing device comprises an outer shell or casing 1 of general circular cross-section. In the preferred construction, the casing includes a tapered front end section 2, an intermediate body section 3 having a substantially uniform outer dimension throughout its length, and an outwardly extending rearward end section 4. If desired, however, the front end section, intermediate body section and end section can all be continuously tapered to give the device a projectile shape. In addition, the rearward end section may either be flared outwardly as shown in FIGS. 1 and 4 or constructed as shown in FIG. 5.

The front end section of the casing is provided with an opening 5 through which a boring or cutting implement 6 extends. This implement is provided at its forward end with a cutting surface 7 extending substantially transversely of the longitudinal axis of the burrowing device.

A flat surface when provided with cutting edges will readily keep the burrowing device on a straight path as it burrows its hole even where the ground conditions are such that obstructions are encountered in the path of movement of the burrowing device. With a pointed end, the burrowing device, if it were to strike a large rock along the edge thereof, might tend to veer off the path while the flat surface 7 shown in FIG. 1 will more readily cut its way through the rock and maintain its movement along the desired straight path. The rearward end of the cutting implement 6 is provided with an enlarged head 8 defining an anvil wall 9. The implement '6 is held within the front end section 2 of the casing by engagement of the head with the restricted wall section 10.

The inner wall of the casing 1 defines a chamber 11 within which there is positioned a piston 12 adapted to move back and forth therein under the influence of compressed air as more fully described below.

The forward face 13 of the piston which is adapted to strike against the anvil wall 9 is cut to form a shallow groove 14 of arbitrary shape as shown in FIGS. 6 and 7. This groove may be of constant or variable depth and provides an indicator by which the length of time the burrowing device has been in service can be ascertained. This makes it possible, for example, to determine whether the device has been in use over and above any time limitations that might be covered by a guarantee or warrantee. During operation of the device, the piston upon striking the anvil will produce a wearing and plastic deformation of the pistons forward face which will in turn decrease the depth of the groove 14 or cause partial disappearance of the groove if it is variable in depth. By appropriate pretesting, it is possible to establish a relationship between the changes in the depth of the groove 14 and the length of time the device has been used.

Although the groove 14 is shown as being provided on the piston, it may alternatively be provided on the anvil wall 9, if desired. In addition to the piston, a cylindrical sleeve 15 is positioned within the chamber 11 defined by the inner wall of the casing 1. The forward end of this sleeve defines a bushing 16 through which the piston moves in sliding, air-tight engagement. The bushing is provided with a radially extending section 17 and is externally threaded at either end as shown at 18 and 19. Complementary threads are provided on the casing sections 2 and 3 whereby these casing sections may be threaded onto the bushing to lock the bushing and inner sleeve in axial alignment within the casing.

Grooves 20 are provided on the inner surface of the bushing and extend about the periphery thereof to facilitate lubrication between the piston and the bushing. In addition, the bushing, as shown in FIG. 8, is provided with transitional surfaces 21 axially outwardly of the grooves 20. These transitional surfaces taper from the intermediate portion of the bushing 16 in a direction away from the internally sliding piston 12 and create a hydrodynamic condition for lubrication which improves the lubricating of these parts and thereby reduces wear of the mating surfaces. These tapered surfaces also improve the resistance to seizure between the piston and bushing during reciprocation of the piston.

In a like manner and for the same purposes, the rearward end 22 of the piston 12, shown in FIG. 9, is provided with similar grooves 23 and tapered surfaces 24 for cooperating with the opposed sleeve 15 and the duct member 25 during reciprocation of the piston relative to the sleeve and duct as more fully described below.

The forward end of the cylindrical sleeve 15 by way of the bushing 16 forms an air-tight sealing fit with the piston 12; and in conjunction with the rear end 22 of the piston functions to divide the chamber 11 into two subchambers, namely a forward chamber 26 and a rearward chamber 27. Extending coaxially through the rearward chamber 27, there is provided a cylindrical duct 25, the forward end of which extends into a duct 28 extending coaxially through the piston 12. Duct 28, in turn, communicates with the forward chamber 26 through ports 29 provided at the forward end of the piston as well as through the extreme front end of the piston. The purpose of this construction is to maintain open communication between the forward chamber 26 and the duct 25 even when the piston is in contact with the anvil wall 9.

A source of compressed air, not shown, is connected by conventional means such as a flexible hose 30 to a compressed air inlet 31 provided at the rear of the burrowing device. The air inlet 31 leads inwardly to a chamber 32 which is in open communication with the rearward end of the duct 25. This arrangement constantly maintains open communication between the source of compressed air and the forward chamber 26.

Positioned between the chambers 27 and 32, there is provided a valve represented generally at 33 that is adapted to be opened and closed periodically in response to changes in air pressure within the chamber 27. The particular type of valve shown comprises an annular plate 34 adapted to sit upon an annular shoulder 35 which constitutes an integral part of the body portion 36 of the valve. Extending through the body portion of the valve, there are a multiplicity of air ducts 37. These air ducts at their forward end open into chamber 27 and at their rearward end open into an annular chamber 38 which is connected to chamber 32 through a plurality of radial openings 39.

The annular plate 34 is biased in open position away from the shoulder 35 by means of a coil spring 40. The tension of this spring alone is insuflicient to maintain the valve in open position against the force of compressed air in chambers 32 and 38. However, when aided by the force of the compressed air in chamber 27, as exerted through the air ducts 37 against the valve plate, the plate is moved to its open position.

Adjacent the forward end of the cylindrical sleeve 15, there are provided a plurality of exhaust ports 41, uniformly spaced about the circumference of the sleeve and so positioned longitudinally that they are open when the piston 12 is in its extreme forward position so as to permit compressed air within the chamber 27 to exhaust into an exhaust conduit 42 formed in the chamber 11. This exhaust conduit 42 is maintained in open communication with the atmosphere through ports 43.

A screw cap 44 which may comprise a retracting device to which a retracting cable may be attached is threaded into the rear end of the rearward casing section 4. This cap constitutes the rearward end of the device and is provided with an outer surface that is tapered towards the rear of the device. As shown, the maximum dimension of this cap is less than that of the outwardly flared end section 4 of the outer casing.

Starting valve mechanism shown generally at 45 is provided inside the rearward end of the device for initially supplying the compressed air to the chamber 27 to start the device; and this initial passage of compressed air to this chamber only occurs when the piston is in its rearward position. As evident from FIG. 1, starting valve 45 is initially held in its forward position closing the openings 39 by means of the coil spring 45'. The pressure of compressed air thus drives piston 12 to its rearward position. When the piston is moved to its rearward position and the pressure of the compressed air increases, the valve 45 opens due to the forces exerted against it in opposition to the spring 45. This opens the ducts 39 to the chamber 27 and the device thus starts to operate.

For permitting unobstructed rearward withdrawal of the burrowing device after it has burrowed, the desired hole in the ground, an expander sleeve 46 is releasably positioned over the outer casing in engagement with the outwardly extending end section 4. This expander member is provided with an inner wall surface 47 which is complementary in shape to the surface presented by the outwardly extending end section 4 of the outer casing.

The expander sleeve shown in FIG. 3 is adapted to be used with a burrowing device having an outwardly extending end section 4 as shown in FIG. 1. It is to be understood that the particular shape of the inner wall surface of the expander sleeve will generally conform to the shape of the rear end section 4 of the device as is clear from FIGS. 4 and 5.

In each case, the expander member is provided with an outer wall surface 48 that is tapered in a direction facing the front end of the device. The maximum outer cross-sectional dimension of the expander member is greater than that of the outer casing whereby the expander member will effectively function to control the cross-sectional dimension of the hole burrowed by the burrowing device.

In operation, assuming that the valve 33 is in open position and the piston 12 has moved to the rear of chamber 27 thereby closing the exhaust ports 41, the force of the compressed air being fed through the air inlet 31 is applied against both the forward and rearward ends of the piston. As shown in the drawings, however, the forward end of the piston is of a smaller effective area than the rear end. Accordingly, the piston will be driven forward and strike against the anvil wall 9. As the piston approaches the anvil wall, exhaust ports 41 are opened thus exhausting compressed air from the rearward chamber 27. With the pressure released from the chamber 27, the valve 33 will be closed by the higher pressure in chambers 32 and 38.

Subsequently, as the piston proceeds rearwardly in the chamber after effecting a forward driving stroke, ports 41 will become closed by the body of the piston and the resulting reduction in volume of the air in chamber 27 will cause an increase in pressure in this chamber which will result in the re-opening of the valve 33 to thereby permit the compressed air supplied through the openings 39 to enter chamber 27 and thus again drive the piston forwardly until it strikes the anvil wall 9.

Throughout the operation of the burrowing device, the forward chamber 26 is maintained in open communication with the source of compressed air and consequently, the air pressure within the forward chamber is maintained substantially constant, advantageously within the range from about 3 /2 to about 6 atmospheres.

Obviously, the constant rearwardly-directed forces exerted against the piston by the compressed air in the forward chamber must be substantially less than the forces periodically exerted upon the piston in a forward direction by the compressed air in the rear chamber.

This differential in these forces is effected by the abovementioned difference in the effective cross-sectional area of the forward end of the piston relative to the effective cross-sectional area of the rear end of the piston.

After the burrowing device has completed its burrowing operation and it is desired to retract the device through the burrowed hole, it is merely necessary for the operator to pull on a cable which has been previously attached to the device at its rear end. If, during this retraction the burrowing device encounters any considerable resistance along the wall portions of the burrowed hole, the expander member will be the first structure to be stopped in its rearward movement due to its larger cross-sectional dimension. When this occurs, further pulling on the cable will cause the radially spaced rear end of the expander to dig into the wall surface of the burrowed hole and thereby effect a release of the expander member from engagement with the outwardly extending rearward end section of the casing. After this has occurred, the burrowing device will readily slip backwards through the expander member leaving the expander member within the burrowed hole, and further retraction of the burrowing device, now without the expander member, can therefore be effected since the outer dimension of the device is now smaller than the dimension of the burrowed hole.

In the situation where it is necessary to rely upon the removal of the expander member to effect retraction of the burrowing device, such member is, of course, lost in the burrowed hole. In order, however, so as not to lose the expander member unless an inordinate amount of resistance is encountered during attempted retraction of the device which would actually prevent such retraction, the cooperating surfaces of the expander member and outer casing can advantageously be made so that a wedging effect is produced as the device is driven forward to tighten the expander member onto the outer casing. By controlling the contour or shape of these cooperating surfaces, the amount of tightening can be varied. With reference to the drawings, it will be apparent that the construction shown in FIG. 1 will produce a wedging effect during forward movement of the device while the embodiment shown in FIG. 5 will not. With the expander member tightened onto the outer casing, as caused :by the abovementioned wedging action, it will readily remain on the burrowing device, and thus be reusable, unless a large opposing force is encountered upon retraction of the device.

Although the above-detailed description of the present invention has been given with reference to a. ground burrowing device which is driven under power in only the forward direction, it is to be understood that the expander member included with such a device has equal application with burrowing devices such as disclosed in the above-mentioned US. Patent No. 3,137,483 that are operated under power in both directions.

I claim:

1. A ground burrowing device having all movable driving elements enclosed therein, said device comprising in combination:

(a) an elongated outer casing having:

(1) a tapered forward end section to facilitate driving through the ground,

(2) an intermediate body section, and

(3) an outwardly extending rearward end section facing said body section and having an outer dimension greater than that of said forward end and body sections;

(b) an elongated chamber housed within said outer casing and extending along the longitudinal axis of said device;

(c) a piston reciprocably positioned within said chamber for back and forth movement along said axis;

(d) at least one anvil wall in said chamber extending transversely of said axis and against which said piston may strike to urge said device in the same direction as that of said piston as it strikes said wall;

(e) a compressed air conduit leading from said chamber to the rear end of said device and adapted to be connected to an extraneous source of compressed air;

(f) valve control means for controlling the flow of compressed air into said chamber to repeatedly drive said piston against said anvil wall; and

(g) an expander member, having inner and outer walls,

releasably positioned on said outer casing in encircling relationship therewith, and having at least a portion thereof in abutting engagement with the outwardly extending rearward end section of said outer casing, said portion of the expander member being defined by the inner wall thereof having a shape complementary to the outwardly extending rearward end section of said outer casing, said expander member further having;

(1) an inner dimension as defined by its inner wall at least equal to the outer dimension of the forward end and body section of said outer casing, and less than the outer dimension of the outwardly extending rearward end section thereof, and

(2) an outer dimension as defined by its outer wall greater than the maximum outer dimension of said outer casing.

2. A ground burrowing device according to claim 1 wherein:

(a) the outer wall of said expander member defines an outwardly flared surface facing the body section of said outer casing.

3. A ground burrowing device according to claim 2 wherein:

(a) the rearward end of said expander member is spaced radially from the outer casing, and

(b) the inner wall of the rearward end of said expander member tapers toward the front end of said burrowing device.

4. A ground burrowing device according to claim 3 wherein:

(a) the rear end of said burrowing device comprises a cap member having a front end extending into the rearward end section of said outer casing in locked relationship therewith and a rearwardly tapered rearward end of an outer maximum dimension less than that of the rearward end section of said outer casing.

5. A ground burrowing device having all movable driving elements enclosed therein, said device comprising in combination:

(a) an elongated outer housing having a projectile shape and tapered forward end for facilitating driving through the ground;

(b) an elongated chamber housed within said outer casing and extending along'the longitudinal axis of said device;

(c) a piston member reciprocally positioned within said chamber for axial back and forth movement;

(d) at least one concentrically disposed supporting member for supporting said piston member in axial alignment within said chamber;

(e) an intermediate axially extending surface on one of said members in sliding engagement with the other member;

(f) a plurality of circumferentially extending lubricating grooves on said one member spaced inwardly of the ends thereof;

(g) tapered transition surfaces extending from the intermediate portion on said one member toward the opposite ends thereof and away from the opposed surface of the other of said members, said tapered transition surfaces being in continuous radial opposition to the other of said members as the members move axially relative to each other;

(h) at least one anvil wall in said chamber extending transversely of said axis and against which said piston may strike to urge said device in the same direction as that of said piston as it strikes said wall;

(i) a compressed air conduit leading from the rear end of said device and adapted to be connected to an extraneous source of compressed air;

(j) compressed air passageway connecting said chamber to said conduit; and

(k) valve control means for controlling the flow of compressed air into said chamber to repeatedly drive said piston against said anvil wall.

6. A ground burrowing device according to claim 5 wherein:

(a) said intermediate surface and said transition surfaces are separated from each other by said grooves.

References Cited UNITED STATES PATENTS 1,370,031 3/1921 Mangnall 175-19 3,137,488 6 /1964- Zinkiewicz l--19 FOREIGN PATENTS 693,404 9/1964 Canada.

CHARLES E. OCONNELL, Primary Examiner R. E. FAVREAU, Assistant Examiner US. Cl. X.R. 92

Po-ww UNITED STATES PATENT OIPFICE .(s/ss) CERTIFICATE OF CORRECTION Patent No. 3,474,873 Dated October 28, 1969 Inventofls) K? J Zygm-unt 4 It is certified that error appearsflin the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 70 "atmospheres" should read dtmosphere Column 7, line 19 "forward end and body section" should read -forward end and body section Column 8, line 42 "3,137,488 should read --3,l37,483-

SIGNED AND SEALED 'F EB 2 4 I970 Edward H. mm, 1:" I mm sauna m m Malone? of Pa 

